Stabilized organic compositions



Patented July 6, 1954 UNITED, TENT OFFICE Birmingham, Mich, assignors toEthyl Corporation, New York, N. Y., a corporation of Delaware NoDrawing. Application December 9, 1950, Serial No. 200,115

(Cl. M -71) 15 Claims. 1

This invention relates to the stabilization of petroleum hydrocarbons.More particularly, our invention relates to inhibition of attack byoxygen, and the prolongation of the useful life of petroleumhydrocarbons. This application is a continuation-in-part of applicantsco-pending application, S. N. 135,043, filed December 24, 1949, nowabandoned.

Petroleum hydrocarbons comprise a. broad field of industrially valuablematerials. Among the more important uses are included motor fuels,heating fuels, lubricants, solvents, and chemical intermediates. In allthese fields the problem of protecting such materials from attack byoxygen during separation, manufacture, compounding, blending, storageand use is important and in many instances is essential for successfulutilization of these products. The provision of materials which willfurnish such protection has long been recognized as an urgent need.

Hydrocarbon fuels for use in internal combustion, spark ignition enginesmay be classified broadly into two categories: those manufactured andmarketed primarily for use in automotive engines, and those manufacturedand marketed for use in aircraft engines. Although each type of fuel iscomposed essentially of hydrocarbons, the type and stabilitycharacteristics of the hydrocarbons comprising each differ considerably.For example, typical automotive fuels contain straight and branchedchain aliphatics, olefins, naphthenes and some aromatics, while typicalaircraft fuels are particularly low in olefins. During the refining,manufacturing and. blending processes and during subsequent storage andhandling operations it is unavoidable that these fuels or theiringredients, such as cracked blending stocks, are brought into contactwith oxygen. The result of such contact is the formation, by oxidationor polymerization or a combination thereof, of gummy materials whichinterfere with the efficient utilization of said fuels in the engine.Automotive gasolines are, in general, more susceptible to this type ofdegradation by oxygen than aircraft fuels.

Both automotive and aircraft fuels are commonly blended withtetraethyllead before use. Such blending imposes a further point ofinstability in the finished fuel, since the tetraethyllead issusceptible to some deterioration by contact with oxygen during theblending, storage and handling operations, with consequent formation ofhaze, loss of some antiknock value, and lessened performance in theengine. This point of attack is often overlooked, and is ordinarilyunimportant in automotive fuels, as the protective measures necessaryfor'the base stock are usually more than sufiicient to protect thetetraethyllead. if, however, a stabilizing ingredient were added whichis capable of protecting only the fuel, the attack upon thetetraethyllead would then become apparent. In aircraft fuels theprotection ordinarily must center upon the antiknock additive, as thefuel itself is relatively stable. Furthermore, this phase of the problembecomes relatively more important in aircraft fuels, since thetetraethyllead content of such fuels is generally several times thatpresent in automotive fuels.

In recent years a similar problem of degradation of fuels for use incompression ignition engines has become prominent. As the percentage ofcracked stock in such fuels increases, resulting in a higher olefincontent, the susceptibility to gum formation by exposure to oxygenincreases, by processes of oxidation and polymerization, or acombination thereof, of these unstable hydrocarbon components. Thepresence of such gummy materials interferes with the normal operation ofthe fuel filters and injectors in compression ignition engines, thuslowering the efficiency of the engine.

Heretofore, it has not been possible to protect fuels for internalcombustion engines effectively by means of a single class of substancesagainst the two above-described separate but related deleterious effectsof contact with oxygen during the refining, manufacturing, blending,storage and handling operations. Furthermore, because of thespecifications imposed on fuels by the rigid requirements of present dayengines, particularly aircraft engines, it is essential that anymaterial capable of protecting such fuels against deterioration beeffective in extremely small quantities, on the order of one pound ofadditive per five thousand gallons of fuel, so that secondary problemsdo not arise through their use.

Hydrocarbons for other purposes than motor fuels likewise requireprotection from oxidative degradation. For example, lubricating oils,particularly those containing chemical unsaturation or a high proportionof chemical additives are of greatly diminished utility when oxygenattack occurs, both as regards stability during use, and stability onstorage prior to use. Hydrocarbon solvents, of an unsaturated character,are a further example of the general problem encountered withutilization of petroleum hydrocarbons referred to herein. Furthermore,the tremendous growth of that branch of industrial chemicals based onpetroleum hydrocarbons, through cracl ing, polymerization, condensation,reforming and other synthetic operations has created a need forsubstances which will protect such raw materials prior to and during thesyntheticoperations to which they are submitted. Recently, heating fuelsof liquid hydrocarbon type have required protection from gum-formingdegradation to promote trouble-free operation of the heating devices.

It is a primary object of our invention to provide a class of compoundswhich possesses the ability of inhibiting deterioration of organicsubstances comprising hydrocarbons in the presence of oxygen. A furtherobject of our invention is to retard the deterioration of such organicsubstances which normally are susceptible to attack by oxygen or ozone,and which thereby lose the utility in the service for which they aremanufactured, compounded or employed. A more particular object is torender hydrocarbons and hydrocarbon compositions stable on prolongedstorage or during manufacture or use in the presence of oxygen. Stillother objects will appear hereinafter.

The above objects can be accomplished by practicing our invention whichcomprises adding to hydrocarbon materials a small proportion of asubstance derived from the class of hydroxyand amino-substituted phenylureas and thioureas. Our invention resides not in the determination thatcertain hydrocarbon materials can be treated to prevent oxidativedeterioration, but rather in providing a class of compounds which hasbroad utility in providing such protection.

In general the compounds of our invention can be defined as those whichcontain the grouping wherein R1 is alkyl, aryl, or an aryl groupsubstituted on the ring with an hydroxy, amino or alkylamino radical, R2is hydroxyphenyl or aminophenyl, R3 is hydrogen, alkyl or aryl and X isthe oxygen or sulfur atom. Whenever in the further description of ourinvention hereinafter we refer to the term alkyl, it is to be understoodthat We include straight chain, branched chain and cyclic saturatedhydrocarbon radicals. As examples of straight chain saturatedhydrocarbon radicals we include methyl, ethyl, n-propyl, n-hexyl, andn-octadecyl. As examples of branched chain saturated hydrocarbonradicals we include isopropyl, isobutyl, sec.-butyl, isoamyl and2-methy1hexyl. By cyclic saturated hydrocarbon radical we mean, forexample, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,methylcyclohexyl and diethylcyclohexyl.

To further illustrate the nature of these protective substances thegeneralized formula is presented to depict the substituted ureas andthioureas of our invention wherein X stands for the oxygen or sulphuratom, R3, and R4 represent hydrogen or organic radicals further definedhereinafter, and A refers to the activating groups describedhereinafter. In this generalized formula the numbers inserted in thephenyl radical are for the purpose of naming specific embodiments of ourinvention hereinafter. We have found that such compounds of ourinvention, wherein the activating group, A, of the phenyl radical is inthe ortho or para position with respect to theN'-nitrogen atom, exhibitthe greatest effectiveness and are preferred, although some activity isshown by the meta derivatives. The principal function of the groups R1.R3. and R4 is believed to be to impart the proper balance of theproperties of solubility, miscibility and compatibility to theantioxidant with the hydrocarbon substance which is to be protected.While the principal eifect of these groups is as stated above, R1 can befurther chosen to intensify the action of the principal antioxidantforming groups, and in particular this intensifying action is obtainedby choosing R1 as a phenyl group substituted with one of the componentsA. In general the phenyl substituent, A, which We refer to as anactivating group, comprises amino and hydroxy radicals and hydrocarbonderivatives thereof. Thus, we can illustrate the group A by hydroxy,amino, N-methylamino, N,N-dimethylamino, N,N-diethylamino,N,N-methylethy1amino, bLN-ethylbutylamino, N,N-diisopropylamino, N-dodecylamino, N-cyclohexylamino, N,N-cyclohexylmethylamino, etc. Thus,examples of the hydroxyphenyl and aminophenyl groups of our inventionwhich impart the distinctive anti-oxidant activity to our stabilizingcompounds include p-hydroxyphenyl, o-hydroxyphenyl, m-hydroxyphenyl, 3methyl 4 hydroxyphenyl, Z-pentadecyl--hydroxyphenyl, p-aminophenyl,p-n-butylaminophenyl, p-dimethylaminophenyl, p-cyclohexylaminophenyl,p-methylethylaminophenyl and p-diethylaminophenyl.

Those substituents R1, R3 and R4 which are chosen primarily to impartsuperior solubility properties to the compounds of our invention includealkyl, aryl, aralkyl, and alkaryl groups and substituted derivativesthereof. For example we have obtained good solubility characteristicsand maintained the high antioxidant effectiveness of the compounds ofour invention by various combinations of hydrogen, o-cnlorophenyl,phenyl, naphthyl, tolyl, methyl, ethyl, n-propy1, isopropyl, n-butyl,amyl, pentadecyl, n-octadecyl, cyclohexyl, benzyl, p-ethoxyphenyl,p-methcxyphenyl, and B-hydroxyethyl groups on the N- and N'- nitrogenatoms or on the substituted phenyl radical characteristic of thecompounds of our invention.

While we do not intend that our invention be limited by the choice ofthe groups R1, R3 and R4, in the preferred embodiments of our inventionthese groups do not contain excessive amounts of certain atoms andradicals capable of ofisetting the activating influence of thesubstituted phenyl radicals. For example, excessive amounts of halogenatoms or nitro groups are not preferred, although minor amounts can betolerated.

The compounds of our invention may be further defined by reference tothe following methods of preparation, which, while not restricting thescope of the variations possible in different embodiments of ourinvention, are representative of methods employed by us in preparing thespecific materials described herein.

METHOD I Unsymmetrical disubstituted ureas and thioureas of ourinvention have been prepared by reaction between substituted phenyl oralkyl isocyanates or isothiocyanates, and substituted anilines oralkylamines, one combination of which is represented by the equationwhereinthe symbols have the same me'aning as described hereinbefore. Thereactants are mixed, in an appropriate solvent, at a temperature ofabout 50C. and in a few hours the reaction product crystallizes and isrecovered. By this method for example we have prepared the followingcompounds of our invention: N- (n propyl) N (p hydroxyphenyl) urea, N-phenyl N (p-hydroxyphenyl) thiourea, -N-(noctadecyl) --N(p-hydroxyphenyDurea, N-(ptolyl) N (p-hydroxyphenyl) urea, N-phenyl- N(p hydroXyphenyDurea, N phenyl-N"-'(2- pentadecyl-4-hydroxyphenyl)-urea, N phenyl- N- (3 -methyl-4-hydroxyphenyl) urea,N,N-'-diphenyl-N-(p-hydroxyphenyl) urea, N phenyl- N (p-=dimethylaminophenyl) urea, N-phenyl- N'-(n-buty1) -N- p-hydroxyphenyl)urea, N- (pethoxyphenyl) N (p-hydroXyphenyDurea, n- (n-octadecyl) -'N (pdimethylaminophenyhurea, N-phenyl-N-(o-hydroxyphenyl)urea, N- phenyl N-(p-dimethylaminophenyl) -thiourea, N phenyl N (m-hyclroxyphenyl) urea,N-(pnaphthyD- N (p hydroxyphenyllurea, N-(pchlorophenyl) -N'-(phydroxyphenyhurea, and N-octadecyl-N-phenyl-Nei(p hydroxyphenyl) urea.

METHOD II By this method we have prepared the following examples of thecompounds of our invention: N,N-bis(phydroxyphenyl)thiourea and N,N- bisp-dimethylaminophenyl) thiourea.

METHOD III Certain symmetrical disubstituted ureas of our invention areprepared by warming an aqueous solution of the appropriate anilinehydrochloride with urea. manufacture of N,N-bis(p-hydroxyphenyl) urea.

METHOD IV We prepared certain N-alkylaminophenylureas of our inventionby hydrogen reduction of nitroaromatic ureas in the presence of analdehyde ammonia, the method of reductive alkylation, according to theequation This method is illustrated by the Where 'R is an-alkyl group.By this method we have prepared N- (p-hydroxyphenyl) -N-(p-nbutylaminophenyDurea, and N (p hydroxyphenyl) -N-(p-isobutylaminophenyl) urea.

METHOD V Symmetrical disubstituted ureas of our invention canbe'prepared by treating an aniline with phosgene, according to theequation 2Nin+ C0012 A VA As an example of this method we have preparedN,N'-bis(p-hydroxyphenyl)urea thereby.

The absorption of oxygen by hydrocarbons can be measured directly by thestandard method of .the American Society of Testing Materials fordetermination of the oxidation stability of gasoline (induction periodmethod), ASTM designation: 13525-46, as fully described in part III-A,ASTM Standards for 1946. According to this method the induction periodis the period during which there is no drop in pressure, indicating noabsorption of oxygen when the test material is placed in a testing bombmaintained at a temperature of 100 C. with an initial pressure of 100pounds per square inch gauge of oxygen. The induction period increase(IPI) is the increase in the duration of this period caused by theaddition of a protective substance, and isa direct measure of theprotection afforded by such additive. Thus, the longer the IPI the moreeffective is the stabilizer. On the contrary, certain substances exertapro-oxidant effect in which a negative IPI is obtained, that is, theduration of the induction period, or period of no absorption of oxygen,is less than in the absence of the additive.

:Our invention is illustrated by reference to Table I wherein are listedthe IPI of a number of types of gasoline, as representative of the classof substances which can be protected by our compounds, determined by theabove-described method. To obtain the results shown herein 6 milligramsof the additive was dissolved in 100 milliliters of the. gasoline.Vfhere the solubility charact-eristics of the additive were such thatthis concentration could not be obtained, a small amount of asolubilizing agent, such as ethyl alcohol, was added in amount up to 2per cent of the gasoline.

It is well known in the art of protecting gasoline from oxidation thatthe susceptibility to oxidation of gasoline varies significantly withdifferent types of gasolines. Furthermore, it is likewise well knownthat the efficiency oi any antioxidant, and, therefore, the minimumconcentration required, will vary greatly from gasoline to gasoline.Therefore, in order to show the general applicability of the compoundsof our invention to the solution of this problem, and at the sametime'not present in detail the large amount of'data so obtained, we havelisted in Table 1' the average IPI obtained with from one to five testgasolines. The gasolines used in obtaining the 'data. presented hereinwere all commercial blending stocks or finished gasolines and includedthe: following types: An average response gasoline containing 20 percent olefins and 14 per cent aromatics, the remainder being parafiinsand naphthenes; a gasoline containing approximately 38 per cent olefins,33 per cent aromatics, and the remainder paraffins and naphthenes; agasoline containing 18 per cent olefins and 24 per cent aromatics; ahigh-sulfur gasoline containing 0.21 per cent sulfur; and a gasolinecontaining 28 per cent olefins and 18 per cent aromatics with mediumsulfur content.

The ASTM method employed to illustrate the activity of the compounds ofOur invention as in Table I is a reliable indication of the eificiencyof a stabilizing material within the test limits of plus minutes andminus 10 minutes, Therefore, a compound or substance which produces aninduction period increase of greater than 10 minutes is an effectiveantioxidant, while a material which decreases the induction period bymore than 10 minutes is a pro-oxidant. Materials exhibiting an effectwithin these limits are essentially inert. Thus, referring to Table I,it is readily apparent that compounds 2, 3, 5, 6, 10, ll, 12, 15 and 17,are strong antioxidants, and are typical examples of thehydroxyphenylureas of our invention containing but a single activatinggroup and a diversity of the solubilizing groups. Still further examplesof this embodiment of our invention which possess high activity includeN n octadecyl N p hydroxyphenylurea, N phenyl N (2 pentadecyl 4hydroxyphenyl) urea, N-a-naphthyland N-fl-naphthyl- N phydroxyphenylurea, N phenyl N n octadecyl N p hydroxyphenylurea, and N,Ndiphenyl N p hydroxyphenylurea. Typifying the activity of thehydroxyphenylthioureas of our invention is the compound numbered 4,containing the single hydroxy activating group. A further example ofthis embodiment is N o tolyl N (2 methyl 4 hydroxyphenyl) thiourea.Compounds 7, 16, 18 and 19 illustrate the aminophenyh andalkylaminophenylureas and thioureas of our invention in which onlysolubilizing groups are present in addition to the activating group. Inaddition, N phenyl N p diethylaminophenylurea is a strong antioxidantand a representative of this class. The compounds of our invention inTable I numbered 8, l3 and 14 represent those containing two identicalsubstituted phenyl activating groups. In general, such embodimentsinclude the N,N-bis(hydroxyphenyl)-, N,N-bis- (aminopheny1)-, N,Nbis(alky1aminophenyl) and N,N bis(dialkylaminophenyl) ureas andthioureas. Compound No. 1 in the table shows the extremely highantioxidant efiectiveness obtained b combining two different substitutedphenyl groups on the ureas and thioureas or our invention. Furtherexamples of such an embodiment include compounds No. 9 and 20 as wellas, for example, N-p-aminophenyl-Np-hydroxyphenylurea andN-p-isobutylaminophenyl- N p-hydroxyphenylurea.

Illustrative of the specificity of the abovedescribed activatingsubstituted phenyl groups of the preferred embodiment of our invention,Table I also lists the results obtained when the parent compounds ureaand thiourea were tested by this method (Nos. 21 and 24). Thesematerials are essentially inert as antioxidants. Likewise, incorporatingN,N-phenyl and alkyl groups unsubstituted with hydroxy or amino groupsdoes not impart antioxidant properties to urea and thiourea, asexemplified by Nos. 2'7, 29, 32 and 34. Such compounds range betweeninert materials and strong pro-oxidants. Further examples of suchcompounds which we have found not to be antioxidants includeN,N-dimethylurea, N- phenyl N methylthiourea, and N,N' di n butylthiourea. Furthermore, substitution of the phenyl radical ofphenyl-ureas and thioureas with other groups than the activating groupsof our invention does not produce an antioxidant material. For examplethe nitro group of No. 26 imparts no activity. Still further examples ofsubstituted phenyl-ureas and thioureas which are not antioxidantsinclude N-phenyl-N-(3,5-dichlorophenyl) -urea and N-phenyl-Nmethy1-N'-(3,5-dichlorophenyl)urea. Further, we prefer that the compounds of ourinvention contain a single activating group on each phenyl radical.

To illustrate that there must be one and only one hydrogen atom on theN-atom of our generalized formula of our compounds, the N,N'- tetrasubstituted ureas and thioureas are prooxidants as shown in Table I,Nos. 25 and 35. The latter compound particularly shows the importance ofthis NH- grouping, for in this compound two of the p-hydroxyphenylgroups are also present. The lack of antioxidant effectiveness of ureasand thioureas containing the grouping NHz is illustrated by entries 28and 33 in Table I, even though a p-hydroxylphenyl group is present inNo. 28.

The above contrast in results clearly draws the distinction betweenso-called metal deactivators and the true antioxidants. Many disclosureshave been made to these and similar compounds, that is ureas andthioureas not containing the hydroxyphenyl or aminophenyl, or thosecontaining a free --NH2 group, as metal deactivators, wherein theantioxidant-destroying power of trace amounts of certain metals isnullified, permitting a true antioxidant to function. However, in theabsence of such metals and in the absence of true antioxidants suchmaterials afford no protection to hydrocarbons.

Table I E FFECI ON IND UCTION PE RIOD INC REA SE OF GAS 0 LINE 8 IPI,No. Substance min 1 N-p-Hydroxypheuyl-N-(p-n-bntylamiuophcnyl)- 540urea. N-Benzyl-N-p-hydroxyphcnylurca 390N-n-Propyl-N-p-hydroxyphcnylurea. 350 N-Phcnyl-N-phydroxyphenylthiourec. 280 N-Phenyl-N-phydroxyphenylurea 275N-Phenyl-N'-(3-methyl-4-hydroxyphenyl)urea 255 N Phenyh -plimethylamiuophenyluroa 235 N,N-Bis (p-hydroxyphenyl)thiourca 220N-p-Ethoxyphcnyl-N-p-hydroxyphcnylnrea. 190 N Phenyl-No-hydroxyphenylurea 180 N-o-Chlorophenyl-N-p-hyd roxyphenylur 175N-p-Tolyl-N'-p-hydro.wphenylurea 1 N,N-Bis (p-hydroxyphcnyDllrea 140N,N-Bis(p-dimethylamlnophcnyl) thi0urca 130NPhenyl-N-n-butyl-N-p-hydroxypIlenylurea 100N-n-Octadecyl-N-pdimethylaminophenylurea 8ON-Phenyl-N-m-hydroxypheuylurea N-Pheny1-N-paminophenylurea 65N-Phenyl-N-pdimethylaminopheuylthiourea. 65 N-p-EthoxyphenylN-pdimcthylaminop h c nyl 6n urea. Thiourea 10 N-B-Hydroxyethylurea 1nN-Allyl thiourea 10 Urea 0 N,N-Dimenthyl-N,N-diphenylurea 0N-Phenyl-N-pnitrophenylurea l0 N,N"Diethy1urea 10 N-(n-Butyl)-N-(p-hydroxyphenyl)urea -35 N,N-Diethylthiourea 5O N-Phcnylthiourca. 25N-Phenylurea -50 N,N-Bis(isopropyl)thiou 5O N,N-Bis(phenyl)thiourea. 50N,N'-Bis(phenyl)th1ourea. 70 N,N-Dimethyl-N,N-bis(p ypheny-Dthio- 70urea. N,N-Bis(amyl) thiourea We have demonstratedthe efficiency of thecompounds of our invention in preventing .undue formation of gum inautomotivegasolines by storing, such a gasoline for long periods in thepresence and absence of our antioxidantsand determining from time totime the gum content of the fuel. A comrnereial motorgasoline con-.sisting of 50 per cent straight-run-and 5.0. percent thermally-crackedgasoline initially containing 2.5 milligrams of gum per 100 milliliterswas employed. For each demonstration duplicate amber quart bottles werefilled with one pint of the gasoline and sufficient additive wasdissolved therein to be equivalent to 4.5 milligrams of stabilizer per100 milliliters of gasoline. 1 The bottles were stoppered and stored inthe dark at a temperture of 110 F. Every four weeks the bottles andtheir contentswere cooled to roomiemperature and the stoppers wereremoved for two hours to permit access to the air. Every 8 weeks asample of the fuel mixture was removed and the dissolved gum therein wasdetermined by the air-jet evaporation method, ASTM-designation:D381-416, fully described in ASTM Standards for 1946,Part III-A. In thesame manner the gum formed in the fuel under these conditions, but inthe absence of the antioxidants of our invention, was determined bystoring, aer ating and sampling the untreated fuel as above. From TableII it is readily apparent that the amount of gum formed in the presenceof our stabilizing materials was insignificant, and, furthermore, thatthis protection was afforded to a sensitive fuel, under conditionswhereby very large quantities of gum were formed in the untreated fuel.

Table II EFFECT ON GUM IN MOTOR GASOLINE Increase in gum content,rug/100 ml.

No. Substance To illustrate the protection afforded to hydrocarbonsolutions of tetraethyllead by the com pounds of our invention weconducted a series of tests in which hot-acid isooctane, carefullydistilled from glass equipment, and containing 4.6 milliliters oftetraethyllead per gallon, was heated at a temperature of 160 C. in astainless steel bomb with oxygen added to an initial pressure of 100pounds per square inch gauge. Under these conditions the pressure in abomb containing only isooctane and a tetraethyllead antiknock mixtureunderwent a sharp drop after four hours, indicating absorption of oxygenby the fuel mixture. The minimum concentration of each of severaladditives required to prevent a drop in pressure in a bomb during aperiod of 16 hours at a temperature of 100 C. was thereupon determined.Thus, the effective concentration shown in Table III is the quantity ofadditive required, expressed as milligrams per 100 milliliters of fuel,to afford a greater than fourfold increase in the stability of the fuel.

Table 111 STABILIZATION OF ISOOCTANE CONTAINING TE'IRA- ETHYLLEADEffective No. Additive conc.

mg./ ml.

1. N-(p-hydroxyphenyl)-N-phenylurea 0.2 N-Plienyl-N-(p-l1ydroxyphenyl)thiourea l 0. 4 N-n-Butyl-p-aminophenol 1. 5sym.-Diphenylurea 2. 3 Eth ylenethiourea. 2. 3

By reference to Table III the low effective con centration to produce amore than four-fold increase in the stability of the fuelof thecompounds of our invention is immediately apparent. Comparing Nos. 1 and2, representative of the compounds of our invention, with No. 3,acommercial material widely used to stabilizegasolines, our compoundsare from three and-onehalf, to seven and one-half times as effective. Byfurther comparing Nos. 1 and 2 withNos. 4 and 5 the effectiveness of theactivating groups characteristic of thecompounds of our invention isfurther illustrated. Compounds 4 and 5 failed to protect the fuelmixture when added in amounts of six to eleven times the effectiveconcentrations of representative compounds of our invention.

The quantities of'the compounds of our invention incorporated in thematerials to be stabilized are not critical and depend largely upon thetype of material being stabilized and the conditions under which theexposure to oxygen occurs. For example, with gasolines, diesel fuels,heating oils, gasoline tetraethyllead mixtures, mineral oils,lubricants, hydrocarbon solvents and chemical intermediates, and similarmaterials the compounds of our invention are preferably employed inconcentrations between the limits of approximately 0.1 and 15 milligramsper 100 milliliters of material to be stabilized. For other materialssomewhat larger amounts of the stabilizers of our invention arepreferred and can be tolerated. Thus, in such materials we employbetween approximately 0.1 and 2 parts of antioxidant per 100 parts ofoxidizable material. Thus, our compounds can be satisfactorily employedin a wide range of concentrations, and we do not intend that ourinvention be restricted to the specific quantities mentioned herein.

We have disclosed a number of preferred embodiments of our invention andillustrated several means whereby protection can be afforded tohydrocarbons sensitive to attack by oxygen. Our invention is notintended to be limited to the specific embodiments of our inventionherein or to the means described herein for obtaining the advantagespossible in employing our compounds, as other methods of practicing ourinvent will be apparent to those skilled in the art.

We claim:

1. A petroleum hydrocarbon olefin-containing fuel, for use in internalcombustion engines,

stable to oxidation, consisting essentially of a petroleum hydrocarbonfuel composition, normally tending to deteriorate in the presence ofoxygen and, in quantity sufficient to inhibit such deterioration, anantioxidant ingredient having the general formula 11 wherein R1 isselected from the group consisting of alkyl containing from 1 to 18carbon atoms inclusive, aryl hydrocarbon, hydroxyphenyl, aminophenyl,and lower alkylaminophenyl, R3 is selected from the group consisting ofhydrogen, alkyl containing from 1 to 18 carbon atoms inclusive, andaryl, A is selected from the group consisting of hydroxy, amino, andlower alkylamino, and X is selected from the group consisting of oxygenand sulfur.

2. The petroleum hydrocarbon fuel of claim 1 wherein the antioxidantingredient is a thiourea.

3. The petroleum hydrocarbon fuel of claim 1 wherein the antioxidantingredient is a urea.

4. The petroleum hydrocarbon fuel of claim 1 wherein A is a p-hydroxygroup.

5. The petroleum hydrocarbon fuel of claim 4 wherein the antioxidantingredient is a urea.

6. The petroleum hydrocarbon fuel of claim 1 wherein A is a p-aminogroup.

7. The petroleum hydrocarbon composition of claim 6 wherein theantioxidant ingredient is a urea.

8. The petroleum hydrocarbon composition of claim 6 wherein theantioxidant ingredient is a thiourea.

9. The composition of claim 1 wherein the antioxidant ingredient isN-p-hydroxyphenyl-N (p-n-butylaminophenyl) urea.

10. The composition of claim 1 wherein the 12 antioxidant ingredientdroxyphenylthiourea.

11. The composition of claim -1 wherein the antioxidant ingredient isN,N'-bis(p-hydroxyphenyl) urea.

12. The composition of claim 1 wherein the antioxidant ingredient isN,N-bis(p-dimethylaminophenyl) thiourea.

13. The composition of claim 1 wherein the antioxidant ingredient isN-phenyl-N-p-aminophenylurea.

14. The petroleum hydrocarbon composition of claim 1 wherein A is ap-alkylamino group.

15. The petroleum hydrocarbon composition of claim 14 wherein theantioxidant ingredient is a thiourea.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,266,601 I-Iowland Dec. 16, 1941 2,302,552 Johnson Nov. 17,1942 2,373,049 Pedersen Apr. 3, 1945 2,396,156 Clarkson Mar. 5, 19462,477,872 Haury Aug. 2, 1949 2,657,984 Braithwaite et al. Nov. 3, 1953OTHER REFERENCES Beilstein, 4th ed. (1930), V01. 13, page 101.

1. A PETROLEUM HYDROCARBON OLEFIN-CONTAINING FUEL, FOR USE IN INTERNALCOMBUSTION ENGINES, STABLE TO OXIDATION, CONSISTING ESSENTIALLY OF APETROLEUM HYDROCARBON FUEL COMPOSITION, NORMALLY TENDING TO DETERIORATEIN THE PRESENCE OF OXYGEN AND, IN QUANTITY SUFFICIENT TO INHIBIT SUCHDETERIORATION, AN ANTIOXIDANT INGREDIENT HAVING THE GENERAL FORMULA